1. Field of the Invention
The present invention relates to a process for manufacturing functional composite materials to be shaped into plastic articles, such as fibers, molded articles, biaxially oriented films, or the like, which have been incorporated with fine particles or additives.
2. Description of the Prior Art
Heretofore, the mainstream of composite materials to be processed into shaped articles, etc. has been those comprising a thermoplastic resin compounded by melt-blending or kneading with a filler having a dimension of about 1 .mu.m or more, such as glass fibers, carbon fibers, whiskers or the like (for example, Japanese Patent Application Laid-open No. 61-277,421). These composite materials have posed problems of appearance and impact resistance of the shaped articles that should have been improved. Alternatively, in the case where fine particles having a dimension of less than about 1 .mu.m, such as titanium dioxide, carbon black, magnetic bodies or the like, are dispersed, the mainstream of the process has been those wherein the fine particles are dispersed uniformly by blending during polymerization of the thermoplastic resin. However, such processes have also presented problems such that practically employable fine particles are limited to those with a good heat resistance, such as titanium dioxide, carbon black or the like, due to the high temperature of the reaction system. A great deal of labor and expense are necessitated by installation of an exclusive polymerization equipment as well as cleaning work thereof, due to staining of the equipment. Further, there has been well-known a masterbatching system wherein fine particles or an additive are blend-kneaded in a high concentration. However, this has also presented problems that a great deal of energy and labor is required for drying both the resin before kneading and the masterbatch after kneading and, further, deterioration of the physical properties of the shaped articles due to the thermal history in the kneading step.
In view of these problems presented by the shaped articles made from conventional composite materials, there have been desired the advent of techniques for manufacturing various shaped articles or previously non-existent higher grade articles, such as biaxially oriented films, sheets, fibers or the like from composite materials containing fine particles, having a particle size of a submicron to micron order instead of conventional fillers having a particle size of 10 to several tens of microns. Namely, it is required to develop a novel technique wherein a powder process dealing with the submicron to micron grade fine particles is combined integrally with a polymer process. The powder process and the polymer process are essentially different techniques from each other. The construction of techniques wherein these are harmonized can be achieved by harmonization of pneumatic conveying techniques of the submicron grade fine particles with the polymer processes. For this purpose, there is required a treating or collecting technique of the submicron grade fine particles which matches the polymer processes.
Generally, the typical techniques which have been practiced industrially in the polymer processes are, for example, particle size reduction by means of a sand mill and dust collection by means of bag filters. However, these are not only difficult to make completely continuous as a polymer process but also pose a problem of moisture absorption, re-aggregation or the like of collected fine particles.